The wearing of contact lenses is a popular technique for correcting a variety of vision problems. So-called “soft” contact lenses are particularly popular with wearers because they consist of a high water volume and conform closely to the wearer's eye. This significantly increases the comfort of the wearer, particularly when a contact lens is worn over a long duration.
Like many other medical products, contact lenses are expected to meet high standards for quality and reliability. As part of the quality assurance and quality control (QAQC) procedures in manufacturing contact lenses, specimens from some or all of the manufactured batches are subjected various test processes. This ensures generally that the manufacturing processes are sound and that a stable level of quality is maintained over time. An approach to testing a sample contact lens entails loading it manually or automatically (e.g. robotically) into a fluid-filled (e.g. saline) cuvette, and testing the contact lens. An exemplary cuvette is a glass or polymer tube with a flat transparent bottom. Notably, processes can be properly performed on the subject contact lens if the contact lens rests on the bottom of the cuvette in a concave down orientation, and is not everted (inside out). While the manual or automated loading process makes efforts to ensure the lens is in the desired non-everted, concave-down orientation, there are times when the contact lens is loaded improperly. In fact, there are four possible orientations (“poses”) for a soft contact lens resting on the bottom of a fluid-filled cuvette for any given inspection cycle. These four loaded poses are:
1. non-everted concave down (CCD, good)
2. non-everted concave up (CCU, bad)
3. everted concave down (ECCD, bad)
4. everted concave up (ECCU, bad)
If the contact lens has pose 1 (CCD, good), then it can be transferred to one or more further processes. If the contact lens has pose 2 (CCU, bad), it should be flipped into the correct orientation, requiring further physical action before proceeding to further processes. If the contact lens has pose 3 or 4 (ECCD or ECCU, both bad), it is typically discarded, as it has experienced possible plastic deformation that renders it imperfect.
While it may be possible to determine the pose of a contact lens readily based upon a side view image of it in the cuvette, the processes to which the contact lens is subjected employ a cuvette with opaque or diffusive side walls. It is therefore not practical to obtain a side view of the lens. Rather, only a top or bottom view with front or back lighting of the contact lens is attainable, i.e. a “face-on” view. It is more challenging to determine the pose of the contact lens (either manually or using a vision system application) from this view point.
It is therefore desirable to provide a system and method for determining the orientation/pose of a contact lens with respect to a cuvette in a face-on view, using a vision system that can distinguish between various poses based upon such direct, face-on view of the top or bottom surface of the contact lens. This system and method should allow for relatively quick categorization of the pose so that further processes (if desired) can be employed with respect to the contact lens and should enable the use of commercially available illuminators and vision system components.